Abstract GS3-04: Pathologic complete response (pCR) to neoadjuvant treatment with or without atezolizumab in triple negative, early high-risk and locally advanced breast cancer. NeoTRIPaPDL1 Michelangelo randomized study

Abstract Background: Triple negative breast cancers of high proliferation or grade are a subgroup characterized by very poor prognosis, rapid progression to metastatic stage and rapid onset of resistance to chemotherapy after initial response. As a whole, triple negative breast cancer (TNBC) represents a specific area of medical need, in which new therapeutic approaches deserve appropriate test. Retrospective data showed that a subset of patients have an ongoing immune response within the tumor microenvironment, and that PD-L1 expression is an adaptive method of tumor resistance to tumor infiltrating lymphocytes, which in turn are needed for response to chemotherapy. Overall, the data suggests a role for immune regulation of response to chemotherapy, and support the concept that blockade of immune check-points may favor the achievement of durable response by immune mechanisms themselves, and in combination with classical chemotherapy. Methods: In this multicenter open label study (NCT002620280), a total of 280 patients with TNBC were randomized to neoadjuvant carboplatin AUC 2 and abraxane 125 mg/m2 iv on days 1 and 8, with or without atezolizumab 1200 mg iv on day 1. Both regimens were given every 3 weeks for 8 cycles and were followed by surgery and by 4 cycles of an anthracycline regimen as per investigator choice. The primary aim of the study is to compare event-free survival 5 years after randomization of the last patient. Important secondary aim is the rate of pCR (defined as absence of invasive in breast and lymph nodes). The comparison among treatments will be carried out by a two-sided Cochran-Mantel-Haenszel test, controlling for disease stage (early high-risk vs locally advanced) and PD-L1 expression (positive vs negative). The primary population for all efficacy endpoints will be the ITT (intent-to-treat) population, the safety population is defined as all randomized patients who received at least one dose of either regimen. pCR and safety data will be presented at the meeting. Patients will continue to be followed up to allow for assessing comparative long-term event-free and overall survival analyses. Supported in part by unrestricted grants from Hoffman-La Roche, Ltd, Switzerland and Celgene International Sarl, Switzerland Citation Format: Luca Gianni, Chiun-Sheng Huang, Daniel Egle, Begona Bermejo, Claudio Zamagni, Marc Thill, Antonio Anton, Stefania Zambelli, Giampaolo Bianchini, Stefania Russo, Eva Ciruelos, Richrad Greil, Vladimir Semiglazov, Marco Colleoni, Catherine Kelly, Gabriella Mariani, Lucia Del Mastro, Ilaria Maffeis, Pinuccia Valagussa, Giuseppe Viale. Pathologic complete response (pCR) to neoadjuvant treatment with or without atezolizumab in triple negative, early high-risk and locally advanced breast cancer. NeoTRIPaPDL1 Michelangelo randomized study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr GS3-04.